Screen separation of tar sand



Dec. 11, 1962 E. w. WHITE 3,068,167

scREEN SEPARATION oF TAR SAND Filed Nov. 16, 1959 82 D||.u Ehm-7 f l REcYcLE) p -f( ,S ATTORNEY Stes 3,ti68,167 SCREEN SEPARATION F TAR SAND Edmund W. White, New Shrewsbury, NJ., assigner to Cities Service Research and Development Company, New York, NSY., a corporation of New Jersey Filed Nov. 16, 1959, Ser. No. 853,175 6 Claims. (Cl. 208-11) This invention relates to an improved process for the recovery of hydrocarbon oil from bituminous sand containing the same.

Large deposits of bituminous sands are found in various localities throughout the world. The term bituminous sand is used herein to include those materials comrnonly referred to as oil sands, tar sands and the like.

One of the most extensive deposits of bituminous sands occurs for instance in the Athabasca District of the Province of Alberta, Canada, and extends for many thousands of square miles in thicknesses ranging up to more than 200 feet.

Various methods have been proposed previously `for separating crude oil from bituminous sands such as the Alberta tar sands, but none of these methods has met 4with substantial success. Since the crude oil obtainable from this type of bituminous sand is relatively viscous material having high tar content and relatively low cornmercial value in comparison with other crude oils, successful commercial processes must involve relatively little expense in the separation of crude oil from the bituminous sands. Operating costs of previously conceived methods for separating the oil from bituminous sands have been suiiiciently high so as to discourage commercial exploitation.

The most successful of the previously known methods for separating hydrocarbon oil from tar sands such as the Alberta tar sands have employed the mixing of the bituminous sand with water followed by separation of sand from the mixture. In these processes it has been found that complete separation of the crude oil from the water has presented considerable diliiculty due to the formation of oil-water emulsions resulting in the discarding of a significant quantity of ciude oil `which could not be successfully separated from the water.

In attempting to separate crude oil from bituminous sands considerable difficulty has also been experienced due to the fact that the solids content of bituminous sands such -as the Alberta tar sands consists of particles of varying size and includes substantial amount sof silt in the form of clay and other very line solids particles. In attempting to effect a complete separation of the crude oil from the bituminous sands previous processes have attempted to retain the silt with the remainder of the solids content of the sands and as a result have usually discarded considerable quantities of crude oil along with such silt and sand.

It is an object of the present invention to provide an improved process for the recovery of crude oil from bituminous sand containing the same.

It is another object of the invention to provide an improved process by 4which crude oil and silt may be separated from bituminous sand containing the same with essentially no loss of crude oil with waste sand.

According to a preferred embodiment of the present invention hydrocarbon oil is recovered from bituminous sand containing the same by the process which includes the steps of mixing said sand with liquid hydrocarbon diluent to form a slurry, passing said slurry through a first separating screen to thereby separate therefrom a rst portion of sand particles too large to pass through the openings of said screen and containing entrained hydrocarbon liquid passing the remainder of said slurry through a second separating screen having smaller openings than said first screen to thereby separate from said slurry a second portion of sand particles too large to pass through the openings of said second screen and containing entrained hydrocarbon liquid, separately mixing each of the thus separated portions of sand with water to form slurries of water, hydrocarbons liquid and sand, and treating said last mentioned slurries for removal of hydrocarbon liquid therefrom.

-For a better understanding of the invention reference should be had to the accompanying drawing which is a diagrammatic illustration in which equipment is shown in elevation of a suitable arrangement of apparatus for carrying out a preferred embodiment of the invention.

In the `drawing bituminous sand is introduced into a mixing vessel 11 as indicated by an arrow 12. The bituminous sands treated according to the invention are bituminous sands which contain crude oil and which usually contain silt in addition to the coarser sand particles. For purposes of this application silt may be defined as solids particles which pass thru a mesh screen and may include for instance extremely line sand particles as well as clay or other solids present in the form of particles of this size. Bituminous sands of this type may contain widely varying amounts of silt, but such silt frequently comprises between about 1 and 20 weight percent of the total solids content of the bituminous sand. Similarly the amount of oil in the bituminous sand may vary widely. Typical tar sands from which crude oil is obtained in accordance with this invention frequently contain between about 5 and about 20 weight percent crude oil. ln addition such tar sands frequently contain between about 1 and about 15 weight percent water. Compositions of suitable bituminous sands may, of course, vary over even wider ranges and minor amounts of other ingredients may also be present.

In the mixing vessel 11, the tar sand introduced as indicated by the arrow 12 is thoroughly mixed with hydrocarbon diluent introduced through a conduit 13 and recycle oil introduced through a conduit 14 by suitable means such as conventional mixing paddles 16 carried on a shaft 17 and rotated by a motor 18. Any suitable amount of diluent may be used in forming the slurry in the mixing vessel 11 but between about 1 and aboutS barrels of diluent per barrel of crude oil is preferably employed. Such hydrocarbon diluent should have a specific gravity substantially less than 1.0 and preferably has a gravity between about 20 and about 65 degrees API. Likewise any suitable amount of recycle oil may be used with recycle rates of between about 1 and about 10, more usually between about 4 and about 6 barrels of recycle oil per barrel of crude oil being preferred. If desired additional diluent may, of course, be used in place of the recycle oil, but use of recycle oil is preferred in order to reduce the amount of diluent which must be separated from crude oil.

Slurry formed in the mixing vessel 11 is withdrawn through a conduit 21 and valve 22 and passed to a screen separation vessel 23 through a conduit 24 by a pump 26. The screen separation Vessel 23 contains two or `more screens such as 27, 28 and 29 having successively smaller openings. A portion of the solid material passing through the screen 27 will thus be retained on the screen 28 while a portion of the material passing through the screen 28 will be retained on the screen 29, etc. The screens 27 28 and 29 are preferably o-scllated to facilitate passage of the slurry therethrough and to prevent bridging or plugging by retained sand. Solids particles sufficiently small to pass through all of the screens in the screen separation vessel 23 as well as-most of the liquid contained in the slurry introduced through the conduit 24 pass through all of the screens and may be withdrawn from the vessel 23 through a valve 31 and conduit 32. It is preferred that the last separating screen through which the slurry passes have openings suiciently large so that most of the silt passes through with the hydrocarbon liquid. This material may then be passed via a pump 33 and conduit 34 to suitable purifying equipment shown here as a water and silt removal system. The silt and water removal system 36 may take any suitable form such as one or more conventional settling tanks, electrostatic separating equipment, etc. Water and silt removed' by the system 36 may be withdrawn through a conduit 35. From the water and silt removal equipment 36 a portion of the purified hydrocarbon oil passes through the conduit 14 to the mixing vessel 11 as recycle oil for use as described above while the remainder of the puried oil from the water and silt removal equipment passes through the conduit 14 and a conduit 37 to diluent recovery equipment 38. The diluent recovery equipment may take any suitable form such as conventional distillation towers and serves to separate hydrocarbon diluent from crude oil recovered from the tar sand. `Crude oil product may be withdrawn through a conduit 41 and valve 42 while diluent may be withdrawn through a valve 43 and conduit 13 for use in forming the original slurry as described above.

The portions of sand separated from the slurry by the screens 27, 28 and 29 are removed from the screens and passed by suitable means such as conveyor belts 51, 52 and 53 to suitable mixing vessels such as 54, 55 and 56. Each of these portions of sand has a different size range of particles due to the different sized openings in the screens 27, 28 and 29. Each of portions of sand also contains entrained hydrocarbon liquid andsmall amounts of water and silt. It should be noted, however, that the vast majority of the silt present in the original bituminous sand passes through all of the screens 27, 28 and 29 and is withdrawn with the hydrocarbon liquid through the valve 31. It should also be noted that the amount of hydrocarbon oil entrained with the sand removed on the screens, while significant from an economic standpoint, represents only a small portion of the oil present such as up to about 0.5 percent. Further, this small amount of crude oil is diluted with recycle oil and diluent as described above.

In the mixing vessels 54, 55 and 56 the separate portions 'of sand containing entrained hydrocarbon oil are thoroughly mixed with suitable quantities of water introduced through conduits 57, 58 and 59 to form slurries of sand, water and hydrocarbon oil. Any suitable mixing apparatus may be employed such as conventional stirring rods 61. By separately slurrying the portions of sand vremoved by the various separating screens as described above it is possible to vary the slurrying conditions for each batch of sand so as to insure sucient slurrying without unnecessary waste of water or of the power required for mixing. In order to insure complete mixing 'and thereby insure complete removal of entrained hydrocarbons from the sand particles it is desirable that all of the sand be suspended in the water during the mixing operation. To achieve this it is necessary that the upward velocities in the mixing chamber exceed the terminal settling velocity of the individual sand particles. Since relatively larger sand particles require substantially higher upward mixing velocities than do relatively smaller sand particles, it is obvious that the minimum amount of mixing which would sutice to slurry a relatively line sand will not sutce to satisfactorily slurry a coarser sand. By separately mixing the individual portions of sand in accordance with the present invention it is possible to slurry cach portion under conditions of minimum mixing power and water consumption to assure suicient slurrying while avoiding wasted power such as would be the case if the relatively ne sand particles and relatively coarser sand particles are slurried together. This is especially true if the lsizes of the `openings in the separating screens are so chosen that the majority of sand is separated following initial separation of the relatively coarser sand particles which require relatively more mixing power for proper slurrying with water. The relatively liner particles separated on the remaining screens suchas 28 and 29 may then be slurried with a minimum amount of power appropriate to the size ranges of particles in these respective portions of sand.

The slurries of water, sand and entrained hydrocarbon oil formed in the mixing vessels 54, 55 and 56 are then treated for removal of hydrocarbon oil therefrom in any suitable manner. As shown in the drawing these slurries may be withdrawn through conduits 62, 63 and 64 respectively and passed to a settling pond 66 in which the slurries are allowed to settle to form a lower layer 67 of sand, an intermediate layer 68 of water and an upper layer 69 of hydrocarbon oil. Separate settling ponds for each of the slurries may, of course, be used. The sand may then be removed at intervals by suitable means such as a conventional drag line while the hydrocarbon oil may be removed from the surface of the pond through a conduit 71 and passed via. a pump 72 and conduit 73 to the conduit 34 and thence to the water and silt removal equipment 36 described above. The pond 66 is preferably provided with a bale such as 74 which serves to prevent entry of hydrocarbon oil into the portion of the pond from which water is withdrawn as through a conduit 76 and pump 77 for passage through conduit 57 to the mixing vessels S4, 55 and 56 as described above.

The following specific example illustrates a practical application of the present invention using the process described and shown in the drawing.

EXAMPLE An Alberta tar sand having the properties shown in Table 1 below is fed to the mixing vessel 11 at the rate of 71,760 tons per day.

Table 1 COMPOSITION AND PROPERTIES OF BI'lUMINOUS SAND FEED Crude oil 9.6 weight percent. Water 4.1 weight percent. Solids 86.3 weight percent. Density 120 lbs. per cubic foot.

SIEVE ANALYSIS OF SOLIDS Weight percent Retained on 80 mesh 22.8 Retained on mesh 43.7 Retained on mesh 13.9 Passing 150 mesh 19.6

Hydrocarbon diluent having a gravity of 25 API is introduced into the mixing vessel 11 through the conduit 13 at the rate of 73,640 barrels per day (b.p.d.) at a temperature of 181 F. Recycle oil is supplied to the mixing vessel 11 through the conduit 14 at the rate of 157,300 b.p.d. at a temperature of 181 F. Slurry is withdrawn from the mixing vessel 11 and passed through the conduit 24 to the separation vessel 23 at a temperature of 150 F.

In the vessel 23 the separating screens 27, 28 and 29 having openings of 80 mesh, 100 mesh and 150 mesh respectively. Material retained on the screen 27 is passed via kthe conveyor belt 51 to the mixing vessel 56 as follows:

Tons per day Solids too large to pass through 80 mesh screen-.. 13,390

Likewise material retained on the screen 28 is passed by the conveyor belt 52 to the mixing vessel 55 as follows:

Tons per day Solids too large to pass through 100 mesh screen 25,650 Hydrocarbon oil 230 Silt 65 Water 1,840

Similarly material retained on .the screen 29 is passed via the conveyor belt 53 to .the mixing vessel 54 as follows:

Tons per day Solids too large to pass through 150 mesh screen-- 8,170

Hydrocarbon nil 90 Silt Water 5 65 Tons per day Mixing vessel 56 1,200 Mixing vessel 55 2,720 Mixing vessel 54 980 As mentioned above it is one of the advantages of the present invention that the solids materials to be slurried in the mixing vessels 54, 55 and 56 are of different size ranges. Thus the solids 4to be slurred in the mixing vessel 56 are almost .entirely solids too large to pass through an 80 mesh screen while the solids to be slurried in the mixing vessel 55 comprise mostly solids capable of passing through an 80 mesh screen but not capable of passing through a 100 mesh screen. Likewise the solids to be slurried in the mixing vessel 54 are almost entirely those solids which passed through the 100 mesh screen but were unable to pass through the 150 mesh screen. It is obvious that the smaller solids particles present in the mixing vessels 54 and 55 will not require the same mixing conditions as the relatively larger particles present in the mixing vessel 56. The savings in energy required for mixing slurries in these mixing vessels may be appreciated when it is considered that the terminal settling velocity of the solids particles present in the mixing vessel 54 is only about 1.0 foot per second while the terminal settling velocity of Ithe solids present in the mixing vessel 55 is about 1.8 feet per second and the terminal settling velocity of the solids present in the mixing vessel 56 is about 2.0 feet per second. It is thus apparent that considerably less agitation is necessary to properly slurry the solids in the mixing vessels 54 and 5S than would be needed if the relatively larger particles were present in these vessels.

While the invention has been described above with respect to a preferred embodiment thereof it will be understood by those skilled in the art that various changes and modilications may be made without departing from the spirit and scope of the invention and it is intended to cover all such changes and modifications in the appended claims.

I claim:

l. The process for the recovery of hydrocarbon oil from bituminous sand containing the same which comprises forming a slurry of said bituminous sand `and liquid hydrocarbon diluent, passing said slurry over a first sep. arating screen `to thereby separate a first portion of solids too large to pass through the openings of said screen from the remaining solids and hydrocarbon liquid, passing said remaining solids and hydrocarbon liquid over a second separating screen having smaller openings than said first screen to thereby separate a second portion of solids too large to pass through the openings of said 6 second screen, separately slurrying said portions of solids with water to remove entrained hydrocarbon liquid therefrom, and treating said slurries of solids, hydrocarbon liquid and water lfor recovery of hydrocarbon liquid therefrom.

2. The process for treating bituminous sand containing hydrocarbon oil which comprising mixing said bituminous sand with liquid hydrocarbon diluent to form a slurry, passing said slurry through at least two separating screens having progressively smaller openings to thereby separate on said screens portions of sand having progressively smaller particles sizes and containing entrained hydrocarbon liquid, separately mixing each of said portions of sand with water to form slurries, and treating said last mentioned slurries for recovery of hydrocarbon liquid therefrom.

3. The process for the recovery of hydrocarbon oil from bituminous sand containing the same which comprises forming a slurry of said bituminous sand and liquid hydrocarbon diluent, passing said slurry through a rst separating screen to thereby separate from said slurry a first portion of sand having particle sizes too large to pass through the openings of said screen, passing the remainder of said slurry through a second separating screen having smaller openings than said iirst screen to thereby separate from said slurry a second portion of sand having particle sizes too large to pass through the openings of said second screen, separately mixing each of said separated portions of sand with water under optimum conditions to form slurries of water, solids and hydrocarbon liquids which were entrained in said separated portions of solids, passing said last mentioned slurries to a settling zone in which the same are allowed to settle to form a lower layer of sand, an intermediate layer of water and an upper layer of liquid hydrocarbons and removing said upper layer of hydrocarbon liquid from said settling zone.

4. The process for treating bituminous sand containing hydrocarbon oil, water and silt which comprises mixing said bituminous sand with liquid hydrocarbon diluent to form a slurry, passing said slurry through at least two oscillating screens having progressively smaller openings to thereby separate on said screens portions of sand having progressively smaller particle sizes and containing entrained hydrocarbon liquid, water and silt, separately mixing each of said portions of sand with added water to form slurries, passing at least one of said last mentioned slurries to a settling zone to form therein a lower layer of sand, an intermediate layer of water and an upper layer of hydrocarbon liquid containing silt, withdrawing said layer of hydrocarbon from said settling zone and treating same for removal of silt therefrom.

5. The process for treating bituminous sand containing hydrocarbon oil, water and silt which comprises mixing said bituminous sand with liquid hydrocarbon diluent to form a slurry, passing said slurry through at least two oscillating screens having progressively smaller openings to thereby separate on said screens portions of sand having progressively smaller particle sizes and containing entrained hydrocarbon liquid, water and silt, separately mixing each of said portions of sand with added water t-o form slurries, passing at least one of said last mentioned slurries to a settling zone to form therein a lower layer of sand, an intermediate layer of water and an upper layer of hydro-carbon liquid containing silt, withdrawing said layer of hydrocarbon liquid from said settling zone and treating same for Iremoval of silt therefrom, and treating the remainder of said lirst mentioned slurry for removal of silt therefrom.

6. The process for the recovery of hydrocarbon oil from bituminous sand containing the same which comprises forming a. slurry of said bituminous sand and liquid hydrocarbon diluent, passing said slurry through a irst oscillating screen to thereby separate from said slurry a first portion of sand having particles too large to pass through the openings of said screen, passing the remainder of said slurry through a second oscillating screen having `smaller openings than said rst screen to 'thereby separate from said slurry a second portion of sand having particles too large to pass through the openings of said second screen, separately mixing eachrof said separated portions of sand with water under different optimum mixing conditions to form slurries of water, solids and hydrocarbon liquids which were entrained in said separated portions of solids, passing said last mentioned slurries to a settling zone in which the same are allowed to settle to form a lower layer of sand, an intermediate layer of Water and an upper layer of liquid hydrocarbons, and separately removing each of said layers from said Vsettling zone.

References Cited n the file of this patent UNITED STATES PATENTS 1,327,572 Ryan Ian. 6, 1920 2,885,339 Coulson et al. May 5, 1959 2,910,424 Tek et al Oct. 27, 1959 2,924,565 Stegemeier et al. Feb. 9, 1960 

1. THE PROCESS FOR THE RECOVERY OF HYDROCARBON OIL FROM BITUMINOUS SAND CONTAINING THE SAME WHICH COMPRISES FORMING A SLURRY OF SAID BITUMINOUS SAND AND LIQUID HYDROCARBON DILUENT, PASSING SAID SLURRY OVER A FIRST SEPARATING SCREEN TO THEREBY SEPARATE A FIRST PORTION OF SOLIDS TOO LARGE TO PASS THROUGH THE OPENINGS OF SAID SCREEN FROM THE REMAINING SOLIDS AND HYDROCARBON LIAUID, PASSING SAID REMAINING SOLIDS AND HYDROCARBON LIQUID OVER A SECOND SEPARATING SCREEN HAVING SMALLER OPENINGS THAN SAID FIRST SCREEN TO THEREBY SEPARATE A SECOND PORTION OF SOLIDS TOO LARGE TO PASS THROUGH THE OPENINGS OF SAID SECOND SCREEN, SEPARATELY SLURRYING SAID PORTIONS OF SOLIDS WITH WATER TO REMOVE ENTRAINED HYDROCARBON LIQUID THEREFROM, AND TREATING SAID SLURRIES OF SOLIDS, HYDROCARBON LIQUID AND WATER FOR RECOVERY OF HYDROCARBON LIQUID THEREFROM. 